1. Field of the Invention
This invention generally relates to a spline hub of a damper disk assembly. More specifically, the present invention relates to a spline hub of a damper disk assembly that is used in a clutch disk assembly.
2. Background Information
A clutch disk assembly transmits and cuts off torque between an engine and a transmission. The clutch disk assembly is one of the members that is rotatably mounted on the input shaft of the transmission. The clutch disk assembly includes a spline hub that engages the input shaft of the transmission. Many spline hubs are either hard chrome plated or Kanigen plated to improve the resistance to wear caused due to the clutch operation.
When plated metal peels due to the continuous clutch operation, the spline engagement portion starts to wear rapidly and does not last long. Moreover, waste water processing facilities are needed to prevent environmental pollution of waste water from plating. Since the plating membrane is very thin (normally thinner than 8 .mu.m), once the plating membrane wears out, the abrasion proceeds very fast.
Another method of strengthening the spline hub is to heat treat the spline hub and therefore form a hardened layer which is equivalent to the plating layer in the previous method. However, the tooth form of the spline hub generally requires precise measuring to prevent backlashes. Since conventional heat treatment generally causes dimensional change due to deformation from heat, a heat-treated spline hub cannot meet the accuracy requirement of dimension. If a polishing process is added after the heat treatment, the accuracy requirement will be met, but it adds to the number of processes and the cost, which makes the heat treatment a less preferable option than plating.
In view of the above, there exists a need for a spline hub of a damper disk assembly that is especially useful in a clutch disk assembly which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.